In the current proposal our goal is to clarify in human volunteers the relationships between hepatic very low density lipoprotein triglyceride (VLDL-TG) output, the uptake of free fatty acids (FFA) by the liver, hepatic fatty oxidation, and de novo fatty acid synthesis. We will also investigate the role of de novo fatty acid synthesis in controlling VLDL- TG output. We will assess these processes using a combination of stable isotope tracer techniques and the net splanchnic balance technique. Various experimental protocols will involve the control of plasma FFA, glucose and insulin concentrations.